If you’re buying a custom ski, you’re going to need to know how ski shape and ski length interact. Here’s your guide.
In the straight ski days of yore, all you really needed to think about was length. Sidecut and rocker have changed that. Now, you need to know how these three fundamental ski shapes interact in order to design the perfect ski for you. (In Part 1 of this series, we covered how to choose a ski’s width. In Part 3, we cover the materials you’ll want the ski to be made of.)
The terms “rocker” and “reverse camber” are often tossed around together, but they basically mean the same thing—a curve that lifts the tip or tail (or both) off the snow and lets the ski rise out of powder. (Camber is opposite—a slight upward lift of a ski’s waist, delivering more power to the snow contact points near the tip and tail.)
Because rocker brings the spots where a ski contacts the snow closer to the boot, the ski effectively becomes shorter and easier to turn. The more rocker, the easier the ski is to turn and the better flotation it gives. Less rocker helps to initiate the turn, but it’s harder work in soft snow. Some skis have an “early rise tip” which is just a way of saying it’s a traditional, cambered ski with a little bit of rocker in the tip to boost lift and make turning easier. Rocker in the tail helps you smear turns, while less means more powerful, directional, fall line turns.
Sidecut is the “hour glass” shape, or the inner curvature of a ski, that creates the turning radius. The turning radius is the virtual circle that a pair of skis makes on edge. The deeper the sidecut, or the more “shapely” a ski is, and the tighter the radius of the turn. The shape, length and width or a ski determines how long or short of a turn the ski is designed to make. A sidecut with a 12- or 14-meter turning radius makes for quick, slalom turns, while a 16- or 20-meter, GS-style sidecut is designed for bigger arcs.
There are multiple sidecut variations. For example, a ski with drastic sidecut, like a slalom or super-carving ski, will have a large tip, narrow waist and tail that’s slightly narrower than the tip. These skis can make tight, sharp turns but are less stable at speed. The bulk of skis in the market, however, have a moderate amount of sidecut. They have less drastic dimensions compared with the carvers and are designed to blend the ability to make short and medium sized turns while retaining some stability at speed. A mild sidecut, as found in mogul or GS skis, allows skis to maneuver tight troughs or make long, fast arcs.
The most variations with sidecut design have occurred with powder-specific skis. A 5-point sidecut, though not limited to powder skis, essentially has five “points” that make up the sidecut dimensions. Both the forebody and the upper tail area make up the widest parts of the ski. The tips and tails are often radically rockered, so the widest dimensions make up the ski’s contact points with the snow—along with the waist. Reverse sidecut, where the widest dimension is in the waist, provides flotation but no hard snow performance, so it dramatically reduces a ski’s versatility. “I prefer some sidecut in a powder skis so I can make shaped arcing turns close to the fall line with my feet under the surface,” says Bob Gleason. “Less sidecut gives more float and keeps the skis closer to the surface.”
There’s no easy rule of thumb for how long a ski should be. The right length has to do with a skier’s height, weight, skiing ability and the ski’s shape. Generally speaking, the longer the ski, the more stability it will have at speed, but the tougher it will be to turn quickly. Conversely, the shorter the ski, the easier it is to turn but its stability at speed decreases.
Your average, everyday alpine skier who is sticking mostly to groomed trails will generally be best with a ski that does not reach over their head. But if there is some rocker in the tip or tail, the ski can be 5 to 10 cm longer than your everyday size. “The more rocker you have, the further down the contact point is, so you can size up. If it’s only slightly rockered, stay with your normal length,” advises Klomparens.
Mogul skiers, and those who ski a lot of tight trees, will prefer moderate lengths, according to Gleason. Beginning skiers and park skiers will do best with shorter skis, which are easier to turn and spin.
Besides the major factors of width, length, sidecut, and rocker, there are other, minor design elements that can influence a ski in more subtle ways. Ski shapes like blunt nose, pin tail, flat tail and tapering at the end of the ski all affect turn shape and ski performance.
A ski with a blunt nose increases the volume of the ski tip and improves float without adding length or swing weight. A “pin tail” is a tail that is tapered and slightly rounded so that the ski is easy to release out of the turn and adjusts easily to different turn shapes. A flat tail—with straight edges—extends the sidecut into the tail for better edge hold and grip. Twin tip skis have dual turned up tips and tails, which create a loose, playful feel. The turned up tails allow the ski to exit the turns easily.
Got it? Now comes the hardest part—what should go inside your dream ski. For that, check out our Custom Ski Guide — Part 3: Choosing Ski Materials.